Device for intercom network

ABSTRACT

The invention relates to, among others, a network device ( 10, 11, 12 ) for an intercom network ( 13 ) for permitting an audio communication, in particular a duplex audio communication with other users ( 14   a,    14   b,    14   c,    14   d,    14   e,    14   f ) of the intercom network, comprising a housing ( 33 ) and a communication module ( 20   a,    20   b ) arranged therein or thereon, with which a radio link can be established for the transmission of audio signals to another user, wherein the radio link is subject to the DECT protocol. The speciality, among others, consists in that the network device ( 10, 11, 12 ) comprises a means ( 21 ) for preventing or reducing multipath interferences.

The invention relates to a network device for an intercom networkaccording to the preamble of claim 1.

Such network devices permit operation in a duplex listening and talkingmode for audio communication with other users of an intercom network.

A network device of this kind in terms of the preamble of claim 1 isgenerally called an intercom station. A difference is made betweenstationary intercom stations and mobile intercom stations, such as thoseattached the belt of a person (belt packs).

An intercom network may comprise one or more stationary users and one ormore mobile users. Also known are intercom networks that comprise onlystationary or only mobile users.

The users are connected to each other by means of so-called switchingcenters.

Network devices according to the preamble of claim 1 have been developedand marketed by the applicant for a long time and are being used inrespective intercom networks. In acknowledgment of the state of the artreference should be made to the applicant's German patent applicationsDE 10 2014 011 963 [US 2016/0050505], DE 10 2016 123 966 A1 and DE 102016 123 968 A1, the disclosure content of which is herewith included inthe content of the present patent application also for the purpose ofincluding one or more of the characteristics.

The known network device according to the preamble of claim 1 comprisesa housing containing a communication module. The communication module isa commonly used commercially available electronic module that canestablish a radio link to other users of the intercom network. A radiolink to other users can be established by means of the communicationmodule that serves the transmission of audio signals. Insofar the radiolink permits a bidirectional transmission of audio signals.

Duplex audio communication, i.e. bidirectional transmission of audiodata between individual users, insofar as wireless, takes place via thisradio link.

The invention only relates to those network devices that are designed tofacilitate a radio link according to the DECT protocol or to anotherprotocol. The DECT protocol in the eyes of experts generally denotes aninternational telecommunication standard using radio technology that hasbeen developed for cordless telephones. The DECT radio standard isdesigned for the telephony inside of buildings with a range of about 50meters maximum. Data transmission is based on a so-called “time divisionduplex” as well as “time division multiple access and frequency divisionmultiple access” method. The predominantly used frequency range isbetween 1880 and 1900 MHZ. Extension frequency bands also exist infrequency ranges between 1900 and 2480 MHZ.

Other protocols in terms of this patent application are protocols thatpermit a corresponding radio signal transmission in the frequency rangesVHF, UHF, 2.4 GHz or 5.8 GHz.

In order to avoid repetitions the term DECT protocol in terms of thispatent application is to be understood in a broader sense and inaddition to the actual DECT frequency ranges also comprises VHF, UHF,2.4 GHz and 5.8 GHz frequency bands/frequency ranges.

Generic network devices for intercom networks are used in intercomnetworks that in particular are used temporarily, also in or onbuildings, in particular in large halls. A number of generic mobilenetwork devices of the generic kind may be used simultaneously.

In some application cases in which known network devices of the generickind are operated, interferences may occur in the communication betweenthe users of the intercom network.

Based on these facts it is the requirement of the invention to furtherdevelop a network device according to the preamble of claim 1 in such away that these interferences are avoided.

This requirement is met by the invention with the characteristics ofclaim 1, in particular with those of the characterizing part, and istherefore characterized in that the network device comprises a means forpreventing or reducing multipath interferences.

The principle of the invention consists in assigning a means to thenetwork device that prevents or reduces possible multipathinterferences.

This means comprises a device for signal correction in order to preventor to reduce the multipath phenomenon.

The invention recognizes that in certain application situations a radiolink between two wirelessly connected users of the intercom networkleads to the generation of a number of radio paths.

As such a first radio path for example may be established between afirst network device and a second network device along the shortestroute (line of sight) between these two network devices.

Since however the emission of the radio signals does not follow along astraight line like for example a laser beam, but propagates along apossibly very large solid angle range, part of the emitted signaloutput—while forming and following a second radio path or track—may betransmitted from the transmitting network device to the receivingnetwork device in such a way that it is reflected from a buildingsurface. In other words these radio signals reflected such are alsotransmitted, but along a second radio path between these two networkdevices.

This multipath propagation (or phenomenon) that is known as such, can inparticular occur in large halls, and further, in particular, with largedistances between network devices connected with each other via a radiopath, and in particular when operating an intercom network with amultitude of network devices. With a network device that receives theradio signal, this results in a superimposition or interference of theintrinsically identical radio signals received from different paths or“tracks” in the state of the art. Due to this interference, for examplecaused by different runtimes or phase shifts, there may occur aconstructive superimposition or destructive superimposition of the radiosignals. The result may be a marked deterioration in signal quality ofthe received radio signals. In certain circumstances this may even causea partial or temporary interruption of the radio link.

The described phenomenon of multipath propagation is known in principlefrom applications other than the one according to the invention, i.e. inparticular from mobile telephones and GPS systems. Proposals are knownfrom these fields of application that have tried to solve this problemelectronically in order to prevent or reduce interferences.

With network devices for intercom networks of the generic kind thatestablish radio links according to the DECT standard, however, no meansare known for reducing or lowering multipath interferences.

Since DECT is a radio standard designed only for cordless telephoneswith only a short range, these problems described above were observed innetwork devices of an intercom network, did not at all occur in cordlesstelephones and other devices that use the DECT radio technology.

The invention realizes that in order to reduce multipath interferences,appropriate electronics can be arranged in the network device.

This can be utilized to solve the problems occurring in the state of theart.

The network device according to the invention may be a mobile, i.e. aportable device worn in particular by a person, or a stationary devicemounted in a fixed position. The network device according to theinvention can, at any rate, establish a radio link to another user ofthe intercom network. Provision may be made for two network devices tobe connected directly with each other by a radio link in accordance withthe DECT standard. The invention also covers the case, however, in whichthe network device according to the invention establishes a radio linkaccording to the DECT standard with another user of the intercomnetwork, e.g. with a switching center or a so-called base or an antenna.By base or antenna is understood a user of the intercom network, viawhich, at any rate, radio signals can be received from, or can be sentto, mobile network devices.

In particular the invention relates to a network device for an intercomnetwork, in which users with portable network devices can move aroundand can establish DECT radio links with other different users of thenetwork at different points in time.

The network device according to the invention permits duplex audiocommunication with other users of the intercom network, in particular itpermits simultaneous operation in a listing and talking mode. Anotherterm for the network device according to the invention is, inparticular, an “intercom station”.

According to the invention the network device comprises a means forpreventing or reducing multipath interferences. This can be done makinguse of intrinsically known methods and intrinsically known componentsused in the art for other purposes such as in mobile telephones. Thiscan be done, but with the proviso of adaptation to the specialfrequencies used in a DECT protocol as well as to the special signalprocessing method that is used in a DECT protocol.

The means provided according to the invention for preventing or reducingmultipath interferences may resort to adaptive filters that are based onthe least-squares-method. The respective information relating thereto isrevealed e.g. in the article “An adaptive multipathestimation/elimination technique for GPS signals reception”, MasateruMinami et al, Electron CommJpan Pt1, 86(1): 74-82, 2003.

Other suitable devices and methods, which the means according to theinvention can use, can be obtained for example from Messrs. Novatel.Information can, for example, be found in “Mattos, Philip G., “Multipathelimination for the low-cost consumer GPS”, Proceedings of the 9thInternational Technical Meeting of the Satellite Division of theInstitute of Navigation (ION GPS 1996), Kansas City, Mo., September1996, pp. 665-671”.

The network device according to the invention, in order to design ameans for preventing or reducing multipath interferences, can alsocomprise devices and methods as described in the article “Eliminatingmultipath fading improves wireless signal reception”, SPIE 7 Aug. 2006by George W. Webb et al.

Furthermore it is possible to obtain commercial components or partsthat—provided they are adapted to suit the DECT method—are suitable forproviding a means for use in the network device according to theinvention, from Messrs. Novatel under the name MET (MultipathElimination Technology) that have been available at least since the year1994.

Finally in order to better understand the technology applicable to themeans of a network device according to the invention reference should bemade to section 22.4.2 “Single-Antenna Multipath Mitigation Techniques”in the Signal Processing for Mobile Communications handbook. Hereadequate descriptions regarding possible method types can be found bothon the principle of the “Narrow Correlator” and on the principle of the“Multipath Elimination Delay Lock Loop” that can both be used inrelation to this means.

Further devices and methods that can be used for a network deviceaccording to the invention and for designing the means, aredescribed—for different applications—in for example the followingpublications: EP 2 244 098 B1, EP 2 215 794 [U.S. Pat. No. 7,652,980],EP 2 211 516 A1, EP 1 982 523 [WO 2007/091821], EP 1 679 818 [U.S. Pat.No. 7,522,682], EP 1 616 368 [U.S. Pat. No. 7,511,675], EP 361 687 [U.S.Pat. No. 5,694,388] and EP 1 221 793 [GB 2,370,952], the content thereofis herewith included in the content of the present patent application inorder to avoid repetition.

According to one advantageous design of the invention the network devicecomprises a loudspeaker and a microphone. This offers the possibility ofproviding the network device as an intercom station and of resorting toknown conventional constructions and designs of network devices.

According to a further advantageous design of the invention the networkdevice comprises at least one programmable or configurable key. Inparticular the network device may comprise a plurality of such keys.

The programmability of the key permits for example providing a directaudio link between the network device and another intercom network userto be selected.

According to a further advantageous design of the invention the networkdevice is designed as a mobile device portable by a person. The networkdevice may in particular be designed as a belt pack or a mobilemicrophone. According to this patent application the belt pack is amobile network device that permits connection to a headset, i.e. amicrophone-headset combination.

According to a further advantageous design of the invention the meanscomprises an RF filter and/or an equalizer. With the aid of thesecomponents it is possible to prevent or reduce multipath interferences.Using these electronic components it is possible to perform a signalcorrection in order to prevent/avoid the multipath phenomenon.

The means according to the invention may for example comprise one ormore equalizers. Equalizers are electronic components that are used inthe art in other applications, e.g. during GSM transmission, for thepurpose of performing a signal correction in order to reduce multipathphenomena.

According to a further advantageous design of the invention the meansuses an orthogonal frequency division modulation process (OFDM) oranother corresponding demodulating process. Electronic components ofthis kind utilizing these processes are also quite well known in thestate of art and are used in order to prevent or reduce multipathinterferences.

According to a further advantageous design of the invention the meansaccording to the invention comprises a Rake receiver. Rake receivers arealso known in the art, albeit for other applications, in order to reducemultipath interferences.

According to a further advantageous design of the invention the means isarranged inside the housing. This permits a compact construction of thenetwork device according to the invention.

According to a further aspect the invention relates to an intercomnetwork according to claim 8.

The invention is based on the requirement to further develop an intercomnetwork of the known kind in such a way that the audio signaltransmission between users is improved.

This requirement is met by the invention with the characteristics ofclaim 8.

In an effort to avoid repetition reference should be made to thestatements above made in relation to the preceding claims. In order tohelp with the understanding of the teaching of claim 8 and theinterpretation and meaning of the characteristics reference should alsobe made the information submitted in claims 1 to 7.

Further advantages of the invention are revealed in the sub-claims notcited as well as in the description below of the embodiments depicted inthe figures, in which

FIG. 1, in a view of a schematic block diagram, shows an embodiment ofan intercom network according to the invention wherein two mobilenetwork devices according to the invention are shown,

FIG. 2, in a partially cut schematic and partially perspective view,shows an embodiment of a network device according to the inventiondesigned as a belt pack, and connected thereto a headset, wherein twodifferent radio paths between the belt pack and a transmitter of theintercom network are depicted, and

FIG. 3, in a schematic view, shows an operator carrying a network devicedesigned as a belt pack according to the invention and a headsetconnected thereto.

Embodiments of the invention are described by way of example in thefigure description hereunder, also with reference to the drawings. Forclarity's sake and insofar as different exemplary embodiments areconcerned, identical or comparable parts or elements or areas are markedwith identical reference symbols, partially with the addition oflower-case letters.

Features that are described only with respect to one embodiment, may beprovided also in any other embodiment in terms of the invention.Embodiments altered in this way are also covered by the invention, evenif they are not shown in the drawings.

All disclosed features are essential, on their own, to the invention.Fully included in the disclosure of the application is the disclosurecontent of the associated priority documents (copy of the preliminaryapplication) as well as of the cited publications and the describeddevices of the state of the art, also for the purpose of includingindividual or several features of these documents in one or in severalof the claims of the present application.

A network device according to the invention is depicted by way of theembodiment in the figures and in its entirety is denoted with 10.

FIG. 2 shows such a network device 10 according to the invention that isdesigned as a belt pack 11. According to FIG. 2 a headset 22 isconnected to the belt pack 11 via a connecting line 25. The headset 22comprises a microphone 23 and a loudspeaker 24.

The belt pack 11, as schematically shown in FIG. 3, may be attached to abelt 32 of an operator 30 by means of a fastening means not shown and beworn by the operator 30.

The belt pack 11 is part of an intercom network 13, the structure andarchitecture of which is illustrated in the block diagram of FIG. 1.

The intercom network 13, in the embodiment of FIG. 1, comprises sixstationary users in total that are marked by reference symbols 14 a, 14b, 14 c, 14 d, 14 e, 14 f. These stationary users 14 are so-calledintercom stations.

Each of the intercom stations 14 a, 14 b, 14 c, 14 d, 14 e, 14 f isconnected via its own connecting line 16 a, 16 b, 16 c, 16 d, 16 e, 16 fwith one of the two switching centers 15 a, 15 b. The switching centers15 a, 15 b may be connected to each other via a connecting line 16.

Each intercom station comprises a microphone-loudspeaker combination.FIG. 1 shows that each intercom station 14 a, 14 b, 14 c, 14 d, 14 e, 14f has its own fixedly installed microphone 17 a, 17 b, 17 c, 17 d, 17 e,17 f. What is not shown in FIG. 1 is that each intercom station 14 a, 14b, 14 c, 14 d, 14 e, 14 f also has its own loudspeaker.

Further, it is not shown in FIG. 1 that each of the intercom stations 14a, 14 b, 14 c, 14 d, 14 e, 14 f comprises a plurality of configurable orprogrammable keys that an operator of an intercom station 14 can actuatein order to establish a direct point-to-point connection with anotheruser at another intercom station 14 a, 14 b, 14 c, 14 d, 14 e, 14 f.

These connection paths are managed by the switching centers 15 a, 15 b.To this end each switching center 15 a, 15 b comprises at least onecontrol 18 a, 18 b that handles the respective switching work.

The stationary users 14 a, 14 b, 14 c, 14 d, 14 e, 14 f are, as the nameindicates, arranged in a fixed place and not designed to be moved. Theintercom network 13 as per FIG. 1 comprises also however a random numberof mobile users, that is mobile network devices.

This includes the initially described belt pack 11 shown in FIG. 1 butalso a mobile microphone 12 as shown in FIG. 1. Mobile network devices11, 12 can be worn by operators 30 and moved by the operators. Whilst inparticular the switching centers 15 a, 15 b are stationary, i.e.arranged in a fixed place, the operators can be moved at random duringan event within range of the intercom network 13.

A mobile network device 11, 12 is able to enter into a radio link withdifferent switching centers 15 a, 15 b or other users of the intercomnetwork 13 at different points in time.

In order to be able to establish such a radio link between a mobilenetwork device 11, 12 and another user, e.g. 15 a, 15 b of the intercomnetwork 13, a communication module 19 a, 19 b is arranged at each of thetwo switching centers 15 a, 15 b. A corresponding communication module20 a, 20 b is also arranged in each mobile network device 11, 12.

The mobile network device 10 in form of the belt pack 11 may for exampleestablish a radio link to the switching center 15 b. To this end thecommunication module 20 a of the belt pack 11 enters into a radio linkwith the communication module 19 b of the switching center 15 b. Theradio link is subject to the DECT protocol. Audio signals can bebi-directionally transmitted via the radio path.

When the belt pack 11 is moved by the operator 30, the belt pack 11 can,at a later point in time, also enter into a corresponding radio linkwith the communication module 19 a of the second switching center 15 avia the communication module 20 a.

FIG. 2 illustrates that the radio link between a belt pack 11 and anantenna 31 is affected by a multipath problem.

The antenna 31 of FIG. 2 may for example be provided by one of the twoswitching centers 15 a, 15 b of the intercom network 13 of FIG. 1.Alternatively the antenna 31 may be a further additional element in theintercom network 13 of FIG. 1 that is connected to one of the switchingcenters 15 a, 15 b and that participates in the bidirectional audio dataexchange. Finally the antenna 31 of FIG. 2 may be provided by anothermobile network device 10, in case there is a need for a directtransmission of radio signals between mobile network devices among eachother.

FIG. 2 illustrates that a radio link is achieved by the antenna 31 witha first radio path Pa being provided. The first radio path is the directshortest connection (line of sight) between the antenna 31/thecommunication module of the antenna 31 not shown in FIG. 2 and thecommunication module 20 a of the belt pack 11.

FIG. 2 in addition shows that a second radio path is generated thatcomprises a radio path Pb and a further partial path marked with Pc thatis generated after reflection from the building surface 29.

The first radio path is in total also marked with the reference symbol27, the second radio path with the reference symbol 28.

Both radio paths 27, 28 each connect the antenna 31 with thecommunication module 20 a.

It will be clear to the expert that because of the two different radiopaths 27, 28 an interference of the electromagnetic waves may occur inthe area of the communication module 20 a of the belt pack 11. Theinterference may be constructive or destructive, in particular. Due tothis superimposition signals may be weakened or deleted altogether.

In order to deal with this phenomenon the belt pack 11 according to theinvention comprises a means 21 that is assigned to the communicationmodule 20 a. This assignment may be effected for example in that themeans—as indicated in FIG. 2—is directly connected to the communicationmodule 20 a via a connecting line 35. The means 21 may also be part ofthe communication module 20 a. Alternatively the means 21 may bearranged upstream of the communication module 20 a in the reception pathof the radio signals.

Due to electronic processing of the audio radio signals arriving via thedifferent paths 27, 28, the means 21 can for example, prevent adestructive interference, and/or correct a respective received signaland thereby prevent or reduce the multipath phenomenon.

For example the means 21 of the belt pack 11 according to the inventionmay be able, to detect different radio paths in the first place, toseparate them and e.g. select the radio path 27 with the best signalquality, whilst suppressing the other radio signals arriving via otherpaths 28.

The network device 10 according to the invention in form of the beltpack 11 in FIG. 2 may, similarly to the mobile microphone 12, include aplurality of programmable or configurable actuating elements 26 a, 26 b,26 c, 26 d, 26 e. These may be configured, for example, as keys,switches, a graphic user interface or the like. The network device 10according to the invention, in particular in form of the belt pack 11,may also comprise a display not shown in FIG. 2.

It will be clear to the expert when looking at FIG. 2 that in additionto the two radio paths 27, 28 shown a plurality of further parallelradio paths may develop of course, causing unwanted interference.Equally the expert will realize that the problem of multipathpropagation will increase in line with how many mobile network devices10 are present in the intercom network 13.

According to the embodiment shown in FIG. 2 the means 21 is arrangedinside the housing 33 of the belt pack 11. It is also covered by theinvention if the means 21 is arranged on the housing 33 of the networkdevice 10, 11.

FIG. 2 depicts a DECT radio path from the antenna 31 to the belt pack11. But the expert will recognize that transmission of the radio signalis bidirectional. Consequently the antenna 31 or the alternativelyschematically shown switching center 15 a in FIG. 2 as well as furtheradvantageously any other user of the intercom network 13 that canestablish a DECT radio link for the transmission of audio signals,comprises an appropriate means 21 for reducing or avoiding multipathinterferences.

The network device 10 according to the invention in form of a belt pack11 in FIG. 2 comprises a port 34 for connection to the headset 22. Theinvention also covers network devices that have a loudspeaker or amicrophone arranged directly in or on the housing or assigned to thehousing.

According to the depiction in FIG. 1 a communication module 20 b isprovided on the mobile microphone 12 that corresponds or essentiallycorresponds to the communication module 20 a of the belt pack 11. Inaddition the mobile microphone 12 may also comprise programmable orconfigurable keys 26 e, 26 f, with which certain preliminary settings orconfigurations can be performed.

The microphone 12, above all, serves to transmit audio information fromthe microphone to another user, e.g. to a switching center 15 b.Microphones 12 are, however, also to be regarded as network devices interms of the present patent application that additionally comprise aloudspeaker not shown in FIG. 1 or a port for a loudspeaker not shown.

To this extent the invention covers network devices for intercomnetworks that permit a unidirectional communication with other users ofthe intercom network, but in particular cover network devices that allowa bidirectional communication with other users of the intercom network.

The invention claimed is:
 1. A network device for an intercom networkfor duplex audio communication between users of the intercom network,the device comprising: a housing; a communication module in or at thehousing and that can establish a radio link for transmitting audiosignals to and receiving audio signals from another user, the radio linkbeing subject to the DECT protocol or another protocol, the audiosignals to the communication module being broken by reflection into aplurality of radio paths; and means for preventing or for reducingmultipath interference by: detecting that a received signal istransmitted via the different radio paths, separating the radio pathsand selecting from the separated radio paths the path with the bestsignal quality, and suppressing signal information from all the radiopaths except the selected path with the best signal quality.